Production of [13N]NH3 with ultra-high specific activity

Aqueous solutions of [13N]NH3 were synthesized according to well-known methods using the 16O(p, α)13N reaction under conditions rendering the smallest possible amount of nitrogen-contaminants. The specific activities and radiochemical yields were measured. Factors, affecting the specific activity of [13N]NH3, were investigated using radio-ionchromatography. The achieved specific activities (GBq/μmol) and radiochemical yields (GBq) of [13N]NH3 were 14±2.8 and 0.3±0.1 (TiCl3 method)*, 590±200 and 5.4±1.1 (DeVardaʹs Alloy method), 5500±500 and 12.7±0.1 (ethanol method), and 6200±2700 and 2.8±0.3 (hydrogen method, 3 bar), respectively at 15 μA for 20 min irradiation (*; 5 μA, 5 min irradiation). More than 70% of the N-13 generated with the hydrogen method was of the chemical form [13N]N2.